1. Field of the Invention
This invention relates generally to pipe gaskets, and more particularly, to such gaskets that are used with corrugated pipe, and even more particularly to such gaskets that are also watertight.
2. Description of the Related Art
This invention is directed to the providing of a gasket for use with corrugated pipe. Preferably the type of pipe is plastic, and the dimension of the pipe is 12″ and above. Gaskets for pipe are well known in the art. Gaskets for pipe include James, U.S. Pat. No. 2,882,073, for a gasket used with concrete pipe, and Kleindienst, U.S. Pat. No. 3,493,237, for pipes preferably made of a ceramic material. In both of those patents, a grout is used to effectuate the ultimate seal desired to be obtained. The use of a grout is made possible by the composition of the pipe.
A gasket for a bell and spigot pipe connection for use with a smooth wall pipe is disclosed in Warner, U.S. Pat. No. 3,573,871; Roberts et al, U.S. Pat. No. 4,223,895; and Vogelsang, U.S. Pat. No. 5,324,083. A bi-directional corrugated pipe-rib seal for use with elastomeric pipe is disclosed in Roe et al, U.S. Pat. No. 4,946,206, and a high pressure coupling for corrugated plastic pipe and conduit is disclosed in Claes et al, U.S. Pat. No. 5,415,436.
Even with the evolution of gaskets, a problem arose as technology made it possible to fabricate plastic pipes of a larger diameter. As technology allowed pipes to be made having large diameters, especially those having a diameter of 40″ and above, gasket design kept pace only where the pipes had to keep dirt out of connected pipes. However, in the case of corrugated pipe gaskets, a unique problem presented itself with the larger pipe where the joined pipes were supposed to be watertight, and more particularly where the joining of the pipes occurred on site through the making of field cuts or repairs.
A resilient pipe gasket marketed as the first watertight gasket for use with large diameter corrugated plastic pipe is Gregoire et al, U.S. Pat. No. 6,082,741. While resilient gaskets had been made for use with corrugated pipe having a relatively small diameter, the amount of rubber used in the gasket was proportional to the height of the corrugations. In smaller diameter pipe, the amount of rubber in a gasket that arguably resulted in a watertight gasket seal still made for a gasket which could be stretched over a pipe spigot without too much trouble. However, as pipe diameter increased, especially when the diameter exceeded 40″, gaskets became too stiff, plus the amount of material in these gaskets made it difficult to install on pipe. Consequently, the ability to effectively provide for a watertight seal was adversely impacted.
For example, attempts were made to provide a concrete collar with plastic bell and spigot joined pipe. Of course, this approach entailed additional time and costs where the installation occurred in the field. Additionally, concrete does not typically adhere well to plastic, so there was always the possibility for leakage. An alternative approach was to try to utilize a conventional type of gasket, such as a valley gasket. However, for pipe having larger diameters, the rubber gasket itself could not be easily stretched onto the pipe and would typically require several people to physically install. Realistically, this theoretical solution was not practical. Another alternative has been to join two spigots ends of pipe together. Then a bell-bell coupling and gasket is used, however, a watertight seal can only be obtained if a gasket existed to seal the bell-bell coupling, and such a gasket only currently exists for use with smaller diameter pipe.
It is thus apparent that the need exists for a watertight pipe gasket which effectuates a watertight seal in field cuts of corrugated pipe, especially when the pipe is of a larger diameter, and which gasket is relatively easy and cost effective to use.